Display control device, display control method, and control system

ABSTRACT

A control system is provided with a plurality of input operation devices that send drawing request information for updating display contents at a shared display device, a display control device that is connected to the input operation devices via a communication line, that stores the drawing request information sent from the input operation devices in a buffer, and that updates the display contents in the shared display device on the basis of the drawing request information stored in the buffer. Then, the display control device controls the shared display device so that the display contents based on the drawing request information stored in the buffer are displayed by being updated in order of priority level, which is predetermined for each type of the drawing request information.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a display control device, a displaycontrol method, and a control system.

2. Description of Related Art

In the related art, a display system, such as the one described inPatent Literature 1, in which a shared display server (display controldevice) that controls the display on a shared display device and aplurality of participant terminals (input operation devices) areconnected via a communication line, thus allowing display operationsperformed at the individual participant terminals to be reflected on thedisplay at the shared display server has been disclosed. However, withthe display system described in Patent Literature 1, for each shareddisplay server, only one terminal is granted the right to operatecursor, etc. displayed on the shared display server.

On the other hand, known processing methods for sharing a single displaycontrol device among a plurality of input operation devices include, forexample, time-sharing processing, serial processing, and so on.

Time-sharing processing is a processing method in which a displaycontrol device allocates an operable period to each of the inputoperation devices, thereby sequentially executing processing for theindividual input operation devices.

Serial processing is a method in which a display control devicesuccessively processes the contents of individual operations performedat the input operation devices, and display processing, etc. isperformed in order on the basis of instructions received from theindividual operation devices by updating display content indicated bydrawing request information every time the drawing request informationis received from the individual input operation devices.

CITATION LIST Patent Literature

{PTL 1} Japanese Unexamined Patent Application, Publication No.2004-21595

SUMMARY OF THE INVENTION Technical Problem

However, with the time-sharing processing described above, because theprocessing time allocated to the individual input operation devices isdetermined in accordance with the number of input operation devices,there is a problem in that the time allocated to the individual inputoperation devices decreases when the number of the input operationdevices is increased, which impairs the operational performance.

As described above, with the serial processing, because operation eventsreceived from the individual input operation devices are analyzed at thedisplay control device to successively execute processing for theindividual input operation devices, there is a problem in that aprocessing unit (CPU: Central Processing Unit) of the display controldevice is subjected to a large processing load. In addition, ifoperation events are simultaneously sent from the plurality of inputoperation devices, because the subsequent processing is not executeduntil the preceding processing is completed, real-time responsiveness islost at the input operation device that has sent the subsequentoperation event, which causes a user to experience the poor operationalperformance.

The present invention has been conceived in light of the above-describedcircumstances, and an object thereof is to provide a display controldevice, a display control method, and a control system that make itpossible to maintain real-time responsiveness in updating displaycontents on a shared display device without impairing the operationalperformance for users, even if a large amount of drawing requestinformation is output from a plurality of input operation devices.

Solution to Problem

In order to solve the above-described problems, a display control deviceof the present invention employs the following solutions.

Specifically, a display control device according to a first aspect ofthe present invention is a display control device that is connected to aplurality of input operation devices via a communication line and thatupdates display contents on a shared display device on the basis ofdrawing request information sent from the input operation devices, thedisplay control device including a storage unit that stores multiplepieces of the drawing request information sent from the input operationdevices; and a control unit that controls the shared display device sothat the display contents based on the drawing request informationstored in the storage unit are displayed by being updated in order ofpriority level, which is predetermined for each type of the drawingrequest information.

With the first aspect of the present invention, the display controldevice is connected to the plurality of input operation devices via thecommunication line and updates the display contents at the shareddisplay device on the basis of the drawing request information sent fromthe input operation devices. Then the display control device displaysthe display contents based on the drawing request information been sentfrom the input operation devices and stored in the storage unit, byupdating them in order of priority level, which is predetermined foreach type of the drawing request information.

The display control device is connected to the plurality of inputoperation devices via the communication line. Because of this, thedrawing request information is sometimes sent to the display controldevice in a large amount per unit time. In such a case, it may becomeimpossible to maintain real-time responsiveness in updating the displaycontents at the shared display device. However, because the displaycontents based on the drawing request information stored in the storageunit are displayed by being updated in the order of priority level,which is predetermined for each type of drawing request information, byincreasing the priority level of the drawing request informationindicating display content of importance for a user, as with the presentinvention, it is possible to maintain real-time responsiveness inupdating the display contents on the shared display device withoutimpairing the operational performance for users, even if a large amountof drawing request information is output from the plurality of inputoperation devices.

With the display control device according to the first aspect of thepresent invention, in the case in which real-time responsiveness wouldbe lost in updating the display contents in the shared display device ifthe display contents are updated based on the multiple pieces of thedrawing request information stored in the storage unit, the control unitmay control the shared display device so that the display contents basedon the drawing request information stored in the storage unit aredisplayed by being updated in the order of priority level, which ispredetermined for each type of the drawing request information.

With the first aspect of the present invention, instead of constantlycontrolling the shared display device so as to display the drawingrequest information stored in the storage unit, updated in the order ofthe priority level, the control unit performs this control only whenreal-time responsiveness will be lost in updating display contents at ashared display device if the display contents based on the multiplepieces of the drawing request information stored in the storage unit areupdated. By doing so, the present invention can reduce the processingload on the display control device.

The display control device according to the first aspect of the presentinvention may be provided with a sorting unit that sorts the multiplepieces of the drawing request information stored in the storage unit inthe order of priority level, which is predetermined for each type of thedrawing request information, wherein the control unit may read out themultiple pieces of the drawing request information that have been sortedby the sorting unit and stored in the storage unit, in the sorted order,and may control the shared display device so as to display the displaycontents based on the read-out drawing request information.

With the first aspect of the present invention, the multiple pieces ofdrawing request information stored in the storage unit are sorted by thesorting unit into the order of priority level, which is predeterminedfor each type of drawing request information. Then, the control unitreads out the multiple pieces of drawing request information sorted andstored in the storage unit, in the sorted order, and controls the shareddisplay device so that the display contents based on the read-outdrawing request information are displayed.

By doing so, with the first aspect of the present invention, it ispossible to maintain real-time responsiveness in updating the displaycontents on the shared display device, with a simple configuration andwithout impairing the operational performance for users, even if a largeamount of drawing request information is output from the plurality ofinput operation devices. As an example of a storage unit according tothe first aspect of the present invention, a FIFO (First In First Out)buffer is employed.

In the display control device according to the first aspect of thepresent invention, a predetermined type of the drawing requestinformation stored in the storage unit may be deleted from the storageunit, excluding the most recent drawing request information.

With the first aspect of the present invention, because thepredetermined type of drawing request information stored in the storageunit is deleted from the storage unit, excluding the most recent drawingrequest information, the processing load on the display control devicecan be reduced, and it is possible to better maintain real-timeresponsiveness in updating the display contents on the shared displaydevice without impairing the operational performance for the users.

With the display control device according to the first aspect of thepresent invention, the drawing request information may include cursormovement information that indicates a cursor destination displayed onthe shared display device, wherein the cursor movement information mayspecify the cursor destination by means of an absolute position withreference to a predetermined position on a screen indicated by theshared display device.

With the first aspect of the present invention, because the cursormovement information included in the drawing request informationspecifies the cursor destination by means of an absolute position withreference to the predetermined position on the screen indicated by theshared display device, the display control device does not need tocompute the cursor destination, which reduces the processing load on thedisplay control device. In addition, the cursor movement information canbe designated as the drawing request information to be deleted from thestorage unit.

With the display control device according to the first aspect of thepresent invention, the display control device may be switched either toa first mode, in which first cursor movement information that specifiesthe cursor destination by means of absolute position with reference to apredetermined position on the screen of the shared display device, isused as the cursor movement information, or to a second mode, in whichsecond cursor movement information that specifies a next cursordestination at the shared display device on the basis of an amount ofcursor movement per unit time at the input operation devices withreference to a previous cursor destination, is used as the cursormovement information.

With the first aspect of the present invention, when the processing loadon the display control device needs to be reduced, the first mode isemployed, which uses the first cursor movement information thatspecifies the cursor destination by means of the absolute position withreference to the predetermined position on the screen indicated by theshared display device. On the other hand, when the cursor displayed inthe shared display device needs to be more finely moved, the second modeis employed, which uses the second cursor movement information thatspecifies the next cursor destination at the shared display device onthe basis of the amount of cursor movement per unit time in the inputoperation devices with reference to the previous cursor destinationserve.

The cursor movements displayed on monitor devices provided in the inputoperation devices are reflected in the display at the shared displaydevice.

Because of this, in the case in which the resolution of the monitordevice described above is lower than that of the shared display device,in the first mode, the first cursor movement information in whichabsolute values for the cursor destination in the monitor devices arecorrected on the basis of the resolution difference with respect to theshared display device is sent from the input operation devices to thedisplay control device. Accordingly, in the first mode, because thedisplay control device does not need to compute the cursor destination,the processing load on the display control device can be reduced;however, the cursor cannot be finely moved in accordance with theresolution of the shared display device.

On the other hand, in the second mode, because the second cursormovement information indicates the amount of change in relativepositions with respect to the previous cursor destination on the screensof the monitor device in the input operation devices, the displaycontrol device needs to determine the amount of cursor movement in theshared display device by computing the amount of cursor movement perunit time on the monitor devices described above on the basis of thesecond cursor movement information. Because of this, in the second mode,the processing load on the display control device is increased. However,in the second mode, because the amount of cursor movement can also bemade smaller in the shared display device by making the amount ofrelative cursor movement per unit time smaller on the screens in themonitor devices described above, the cursor can be moved at theresolution of the shared display device.

In order to solve the above-described problems, a display control methodof the present invention employs the following solutions.

Specifically, a display control method according to a second aspect ofthe present invention is a display control method, in which a pluralityof input operation devices are connected via a communication line anddisplay contents in a shared display device are updated on the basis ofdrawing request information sent from the input operation devices, thedisplay control method including controlling the shared display deviceso that the display contents based on the drawing request informationsent from the input operation devices and stored in a storage unit aredisplayed by being updated in order of priority level, which ispredetermined for each type of the drawing request information.

In order to solve the above-described problems, a control system of thepresent invention employs the following solutions.

Specifically, a control system according to a third aspect of thepresent invention is a control system including a plurality of inputoperation devices that send drawing request information for updatingdisplay contents at a shared display device; a display control devicethat is connected to the input operation devices via a communicationline, that stores the drawing request information sent from the inputoperation devices in a storage unit, and that updates the displaycontents at the shared display device on the basis of the drawingrequest information stored in the storage unit, wherein the displaycontrol device controls the shared display device so that the displaycontents based on the drawing request information stored in the storageunit are displayed by being updated in order of priority level, which ispredetermined for each type of the drawing request information.

Advantageous Effects of Invention

The present invention affords an excellent advantage in that it ispossible to maintain real-time responsiveness in updating displaycontents on a shared display device without impairing the operationalperformance for users, even if a large amount of drawing requestinformation is output from a plurality of input operation devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the overall configuration of a controlsystem according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing the electrical configuration of aninput operation device according to the first embodiment of the presentinvention.

FIG. 3 is a block diagram showing the electrical configuration of adisplay control device according to the first embodiment of the presentinvention.

FIG. 4 is a flowchart showing the processing flow of a sorting programaccording to the first embodiment of the present invention.

FIG. 5 is a schematic diagram required for explaining sorting processingaccording to the first embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of a display control device, a display control method, and acontrol system according to the present invention will be describedbelow with reference to the drawings.

First Embodiment

An embodiment of the control system according to the present inventionwill be described below with reference to the drawings.

FIG. 1 is a block diagram showing, in outline, the configuration of acontrol system 10 according to a first embodiment.

As shown in FIG. 1, the control system 10 according to the firstembodiment is provided with, for example, a plurality of input operationdevices 12, which are information processing terminals, a displaycontrol device 16 that is connected to the plurality of input operationdevices 12 via a communication line 14, and a shared display device 18that displays an image on the basis of an image signal output from thedisplay control device 16.

The input operation devices 12 are operation terminals with whichindividual operators manipulate a cursor and perform operations inwindows, which are displayed on a large-screen display at the shareddisplay device 18, and the number provided is, for example, the same asthe number of operators. Then, the input operation devices 12 senddrawing request information, which indicates contents to be displayed onthe shared display device 18, to the display control device 16 via thecommunication line 14.

The above-described drawing request information includes, for example,cursor movement information, which indicates a cursor destination to bedisplayed on the shared display device 18, image drawing information fordrawing images (diagrams such as line, circle, rectangle, and so forth,as well as image data) generated at the input operation devices 12 onthe shared display device 18, click information for executing anapplication by clicking a button or the like over which the cursor isplaced on the shared display device 18, emergency-message displayinformation, created at the input operation devices 12, for causing anemergency message to be displayed on the shared display device 18, andso on.

The communication line 14 is a wide-area communication line provided byelectrical services companies, an internal communication network, suchas a LAN (Local Area Network), and so forth, and they may be wired orwireless.

The display control device 16 controls the shared display device 18 sothat the display contents thereof are updated on the basis of theoperation information input from the individual input operation devices12.

The shared display device 18 is a display device having a liquid-crystalscreen, a plasma screen, or the like, and may be a single-screen displaydevice or a display device in which a single large screen is formed bycombining a plurality of display devices.

FIG. 2 shows the electrical configuration of the input operation devices12.

The input operation devices 12 are provided with a CPU 20 that governsthe overall operation of the input operation devices 12, a ROM (ReadOnly Memory) 22 in which various programs, various parameters, and soforth are stored in advance, a RAM (Random Access Memory) 24 that servesas a work area or the like when the CPU 20 executes various programs,and an HDD (Hard Disk Drive) 26 that serves as storage means (storageunit) for storing various programs and various information.

Furthermore, the input operation devices 12 are provided with an inputdevice 28 that is formed of, for example, a keyboard, a mouse, and soforth, and receives inputs for various operations, a local monitordevice 30 for displaying various images, and an external interface 32that is connected with the display control device 16 via thecommunication line 14 and that sends and receives various information toand from the display control device 16.

The CPU 20, the ROM 22, the RAM 24, the HDD 26, the input device 28, thelocal monitor device 30, and the external interface 32 are electricallyconnected with each other via a system bus 34. Therefore, it is possiblefor the CPU 20 to individually access the ROM 22, the RAM 24, and theHDD 26, to ascertain the operating states of the input device 28, todisplay various images on the local monitor device 30, to send andreceive various information to and from the display control device 16via the external interface 32, and so on.

Individual screen resolutions of the local monitor device 30 and theshared display device 18 may be the same or may be different. The localmonitor device 30 displays the same image as an image displayed at theshared display device 18, and the local monitor device 30 displaysimages based on the information input by means of the input device 28and a cursor reflecting the movements thereof caused by means of theinput device 28.

In addition, the information, cursor movement, and so forth input bymeans of the input device 28 are sent to the display control device 16as drawing request information via the external interface 32.Specifically, the operator who operates the input operation device 12displays images, cursor movements, and so forth that they want todisplay on the shared display device 18 on the local monitor devices 30,and the input operation device 12 sends drawing request information inaccordance with the images, cursor movements, and so forth to thedisplay control device 16 so that the images, cursor movements, and soforth displayed on the local monitor device 30 is reflected at theshared display device 18.

In the first embodiment, there is a set priority level, which ispredetermined for each type of drawing request information. Table 1shows examples of the priority levels corresponding to the types ofdrawing request information, where drawing request information whosepriority level is shown with a smaller value has a higher prioritylevel.

The priority levels shown in Table 1 are set so as to be higher fordrawing request information indicating display content of greaterimportance for users. For example, the emergency-message displayinformation is set to the highest priority level because it is drawingrequest information for displaying an emergency message on the shareddisplay device 18. On the other hand, the click information is set to alower priority level than the cursor movement information because it isinformation for clicking a button or the like over which the cursor isplaced, where it is assumed that the cursor has been moved to theposition of a button or the like according to the cursor movementinformation.

The input operation device 12 according to the first embodiment addspriority-level information, which indicates the priority level describedabove, to each piece of drawing request information and sends it to thedisplay control device 16.

TABLE 1 TYPE OF DRAWING REQUEST INFORMATION PRIORITY LEVELEMERGENCY-MESSAGE DISPLAY 1 INFORMATION IMAGE DRAWING INFORMATION 2CURSOR MOVEMENT INFORMATION 3 CLICK INFORMATION 4

The input operation device 12 according to the first embodimentspecifies the absolute position of a cursor destination on the screen ofthe local monitor device 30 and sends the absolute positions to thedisplay control device 16 as cursor movement information so that thecursor destination can be specified by means of the absolute position onthe screen of the shared display device 18.

For the cursor absolute position, for example, predetermined positionson the screens of the shared display device 18 and the local monitordevice 30 serve as reference positions. In this embodiment, the lowerleft portion of the screen with the coordinate origin at (x, y)=(0, 0)is used as an example of the reference position. In this case, thehorizontal direction from the lower left portion is defined as thex-axis and the vertical direction therefrom is defined as the y-axis,and the x-coordinate value increases rightward with reference to thelower left portion of the screen and the y-coordinate value increasesupward with reference to the lower left portion of the screen.

In addition, in the case in which resolutions differ between the shareddisplay device 18 and the local monitor device 30, because the CPU 20corrects the cursor movement information on the basis of the resolutiondifference between the shared display device 18 and the local monitordevice 30 and sends it to the display control device 16, the displaycontrol device 16 does not need to compute the cursor destination, whichreduces the processing load on the display control device 16.

For example, when the resolution of the shared display device 18 is 4096pixels by 768 pixels, and the resolution of the local monitor device 30is 1024 pixels by 768 pixels, the CPU 20 sets the cursor destinationspecified on the screen of the local monitor device 30 to be four timesgreater in the x-axis direction and sends this information to thedisplay control device 16 as the cursor movement information.

FIG. 3 shows the electrical configuration of the display control device16.

The display control device 16 is provided with a CPU 30 that governs theoverall operation of the display control device 16, a ROM 42 in whichvarious programs, various parameters, and so forth are stored inadvance, a RAM 44 that serves as a work area or the like when the CPU 40executes various programs, and an HDD 46 that serves as storage means(storage unit) for storing various programs and various information.

Furthermore, the display control device 16 is provided with a video card48 that is connected to the shared display device 18 and that outputs tothe shared display device 18 an image signal that indicates an image tobe displayed on the shared display device 18, an external interface 50that is connected to the individual input operation devices 12 via thecommunication line 14 and that sends and receives various information toand from the input operation devices 12, and a buffer 52 that stores thedrawing request information sent from the input operation devices 12.

The CPU 40, the ROM 42, the RAM 44, the HDD 46, the video card 48, theexternal interfaces 50, and the buffer 52 are electrically connectedwith each other via a system bus 54. Therefore, it is possible for theCPU 40 to individually access the ROM 42, the RAM 44, the HDD 46, andthe buffer 52, to give instructions to the video card 48 with regard toimage signal output, to send and receive various information to and fromthe input operation devices 12 via the external interface 50, and so on.

The buffer 52 according to the first embodiment is a FIFO buffer andstores the drawing request information sent from the individual inputoperation devices 12 in the order in which the drawing requestinformation is sent thereto.

Then, the display control device 16 according to the first embodimentcontrols the shared display device 18 so that display contents based onthe multiple pieces of drawing request information stored in the buffer52 are displayed by being updated in the order of the priority level,which is predetermined for each type of drawing request information.Then, in order to control the shared display device 18 in this way, thedisplay control device 16 performs sorting processing in which themultiple pieces of drawing request information stored in the buffer 52are sorted in the order of the priority level, which is predeterminedfor each type of drawing request information, reads out the multiplepieces of drawing request information that have been sorted by thesorting processing and stored in the buffer 52, in the sorted order, andcontrols the shared display device 18 so that the display contents aredisplayed on the basis of the read-out drawing request information.

Next, the operation of the display control device 16 according to thefirst embodiment will be described.

FIG. 4 is a flow chart showing the processing flow of a sorting programexecuted by the CPU 40 when performing the sorting processing, and thesorting program is stored in a predetermined region of the HDD 46 inadvance. This program is started when the operation of the shareddisplay device 18 is started.

First, in Step 100, the external interfaces 32 are in a standby stateuntil the drawing request information is received from one of theplurality of input operation devices 12, and the process advances toStep 102 when the drawing request information is received.

In Step 102 that follows, the received drawing request information isstored in the buffer 52.

In Step 104 that follows, it is judged whether or not real-timeresponsiveness in updating the display contents in the shared displaydevice 18 will be lost or not, and the process advances to Step 106 inthe case of an affirmative judgment, whereas the process advances toStep 108 in the case of a negative judgment.

A situation in which real-time responsiveness will be lost is asituation in which updating of the display contents based on any drawingrequest information among the multiple pieces of drawing requestinformation stored in the buffer 52 is performed after a predeterminedamount of time (for example, one second) or more has passed after thedrawing request information has been sent to the display control device16. In other words, a situation in which real-time responsiveness willbe lost is a situation in which a large amount of drawing requestinformation is sent to the display control device 16 per unit time,which makes the processing load on the CPU 40 a high load.

Because the processing time for displaying contents based on the drawingrequest information can be predicted in advance for each type of drawingrequest information, the CPU 40 can judge whether or not real-timeresponsiveness will be lost by accumulating the processing time of thedrawing request information stored in the buffer 52.

In Step 106, the drawing request information stored in the buffer 52 issorted.

The processing executed in Step 106 will be described with reference toFIG. 5.

FIG. 5(A) shows a case in which a large amount of drawing requestinformation is stored in the buffer 52, making the processing load onthe CPU 40 a high load, and, as an example, cursor movement information1, image drawing information, cursor movement information 2, cursormovement information 3, emergency-message display information, and clickinformation are stored in the buffer 52. It is assumed that varioustypes of drawing request information described above have been sent tothe display control device 16 from the plurality of input operationdevices 12 in this order. Specifically, when the sorting processing isnot performed, the cursor movement information 1, the image drawinginformation, the cursor movement information 2, the cursor movementinformation 3, the emergency-message display information, and the clickinformation are read out in this order, image signals are generated onthe basis of the read-out drawing request information, and the displaycontents at the shared display device 18 are updated.

Then, as shown in FIG. 5(B), the multiple pieces of drawing requestinformation stored in the buffer 52 are sorted in the order of thepriority levels of each type of drawing request information.Specifically, the priority level information added to the drawingrequest information is read out and the individual pieces of drawingrequest information are sorted on the basis of the priority levelinformation. Because the same types of drawing request information havethe same priority level, the same types of drawing request informationare sorted so as to be placed in order of the time at which the drawingrequest information is sent to the display control device 16.

In the example in FIG. 5(B), the emergency-message display information,the image drawing information, the cursor movement information 1, thecursor movement information 2, the cursor movement information 3, andthe click information are sorted into this order.

Furthermore, in the sorting processing according to the firstembodiment, a predetermined type of drawing request information storedin the buffer 52 is deleted from the buffer 52, excluding the mostrecent drawing request information.

In the first embodiment, the above-described predetermined type of thedrawing request information is, as an example, assumed to be the cursormovement information. Accordingly, as shown in FIG. 5(C), the cursormovement information (the cursor movement information 1 and the cursormovement information 2), excluding the cursor movement information 3,which is the most recent cursor movement information, are deleted fromthe buffer 52.

As shown in Table 2, the possibility of deletion from the buffer 52 ispredetermined for each piece of the drawing request information, and, inthe first embodiment, deletion possibility information, which indicatesthe possibility of deletion, is added to the drawing request informationtogether with the priority level information, and the CPU 40 deletes thedrawing request information on the basis of the deletion possibilityinformation.

TABLE 2 TYPE OF DRAWING DELETION REQUEST INFORMATION PRIORITY LEVELPOSSIBILITY EMERGENCY-MESSAGE 1 NOT POSSIBLE DISPLAY INFORMATION IMAGEDRAWING 2 NOT POSSIBLE INFORMATION CURSOR MOVEMENT 3 POSSIBLEINFORMATION CLICK INFORMATION 4 NOT POSSIBLE

Then, once the sorting of the drawing request information, performed inStep 106, is performed, the display control device 16 reads out thedrawing request information stored in the buffer 52 in the sorted order,in other words, in order starting from higher priority levels, generatesimage signals based on the read-out drawing request information, andupdates the display contents at the shared display device 18.

In Step 108 that follows, it is judged whether or not an instruction forending the operation of the shared display device 18 has been input, andthis program is ended in the case of an affirmative judgment, whereasthe process returns to Step 100 in the case of a negative judgment. Theinstruction for ending the operation of the shared display device 18 isinput through, for example, a predetermined input operation device 12assigned to manage the control system 10 or an input device (not shown)provided in the display control device 16.

As has been described above, the display control device 16 according tothe first embodiment is connected to the plurality of input operationdevices 12 via the communication line 14 and updates the displaycontents at the shared display device 18 on the basis of the drawingrequest information sent thereto from the input operation devices 12. Inaddition, because the display control device 16 is provided with thebuffer 52 that stores the multiple pieces of drawing request informationsent from the input operation devices 12 and controls the shared displaydevice 18 so that the display contents based on the multiple pieces ofdrawing request information stored in the buffer 52 are displayed bybeing updated in the order of the priority level, which is predeterminedfor each type of drawing request information, it is possible to maintainreal-time responsiveness in updating the display contents on the shareddisplay device 18 without impairing the operational performance for theusers, even if a large amount of drawing request information is outputfrom the plurality of input operation devices.

Because the buffer 52 according to the first embodiment is a FIFObuffer, by sorting the drawing request information in the order startingfrom higher priority levels, it is possible to maintain real-timeresponsiveness in updating the display contents on the shared displaydevice, with a simple configuration and without impairing theoperational performance for the users, even if a large amount of drawingrequest information is output from the plurality of input operationdevices 12.

Second Embodiment

A second embodiment of the present invention will be described below.

The configuration of a control system 10 according to the secondembodiment is the same as the configuration of the control system 10according to the first embodiment shown in FIG. 1; the electricalconfiguration of input operation devices 12 according to the secondembodiment is the same as the electrical configuration of the inputoperation devices 12 according to the first embodiment shown in FIG. 2;the electrical configuration of a display control device 16 according tothe second embodiment is the same as the electrical configuration of thedisplay control device 16 according to the first embodiment shown inFIG. 3; and therefore, descriptions thereof will be omitted.

The display control device 16 according to the second embodiment can beswitched to either an absolute position mode that uses first cursormovement information, which specifies a cursor destination by means ofan absolute position with reference to a predetermined position on thescreen of the shared display device 18, or a relative position mode thatuses second cursor movement information, which specifies a next cursordestination at the shared display device 18 on the basis of an amount ofcursor movement per unit time in the input operation devices 12 withreference to previous cursor destination.

The processing load on the display control device 16 can be reduced inthe absolute position mode, whereas the cursor displayed on the shareddisplay device 18 can be moved more finely in the relative positionmode.

To give a more specific description, as described in the firstembodiment, the display at the shared display device 18 reflects cursormovements displayed on the local monitor devices 30 provided in theinput operation devices 12.

Because of this, in the absolute position mode, if the resolution of thelocal monitor device 30 is lower than that of the shared display device18, first cursor movement information in which absolute values of thecursor destination in the local monitor device 30 are corrected based onthe resolution difference with respect to the shared display device 18is sent to the display control device 16 from the input operation device12, as described in the first embodiment. Accordingly, in the absoluteposition mode, because the display control device 16 does not need tocompute the cursor destination, the processing load on the displaycontrol device 16 can be reduced; however, it is not possible to finelymove the cursor in accordance with the resolution of the shared displaydevice 18.

On the other hand, in the relative position mode, because the secondcursor movement information indicates the amounts of change in therelative position between the previous cursor destination and the nextcursor destination on the screen of the local monitor device 30, thedisplay control device 16 needs to determine the amount of cursormovement on the shared display device 18 by computing the amount ofcursor movement per unit time on the local monitor device 30 based onthe second cursor movement information. Because of this, in the relativeposition mode, the processing load on the display control device 16 isincreased. However, in the relative position mode, because the amount ofcursor movement can also be made smaller at the shared display device 18by making the amount of relative cursor movement per unit time on thescreen of the local monitor device 30 smaller, the cursor can be movedat the resolution of the shared display device 18.

For example, in the case in which the resolution of the shared displaydevice 18 is 4096 pixels by 768 pixels and the resolution of the localmonitor device 30 is 1024 pixels by 768 pixels, in the absolute positionmode, the CPU 20 generates the first cursor movement information to besent to the display control device 16 by setting the cursor destinationspecified on the screen of the local monitor device 30 to be four timesgreater in the x-axis direction. Because of this, for the cursor on thescreen of the shared display device 18, the cursor cannot be finelymoved in the x-axis direction.

On the other hand, in the relative position mode, by making the amountof relative cursor movement per unit time on the screen of the localmonitor device 30 smaller, the cursor on the screen of the shareddisplay device 18 can be finely moved pixel-by-pixel in the x-axisdirection.

A user may arbitrarily switch between the absolute position mode and therelative position mode. Because the user inevitably moves the cursor onthe screen of the local monitor device 30 slowly when the user attemptsto finely move the cursor on the screen of the shared display device 18,switching from the absolute position mode to the relative position modemay be performed automatically when the amount of cursor movement perunit time on the screen of the local monitor device 30 drops to or belowa predetermined value. With regard to this judgment for this automaticswitching, for example, the CPU 40 in the display control device 16makes the judgment and sends switching information, which indicatesswitching from the absolute position mode to the relative position mode,to the input operation device 12, and, once the input operation device12 receives the switching information, the input operation device 12subsequently sends the second cursor movement information to the displaycontrol device 16.

As above, although the present invention has been described in terms ofthe individual embodiments described above, the technical scope of thepresent invention is not limited to the scope described in theindividual embodiments described above. It is possible to add variousalterations or improvements to the individual embodiments describedabove within a range that does not depart from the spirit of theinvention, and the technical scope of the present invention alsoencompasses forms to which such alterations or improvements are added.

For example, although the individual embodiments described above havebeen described in terms of the case in which the input operation devices12 send the drawing request information to the display control device 16by adding the priority level information, which indicates the prioritylevel, as well as the deletion possibility information, the presentinvention is not limited thereto, and a form in which the drawingrequest information is sent to the display control device 16 from theinput operation devices 12 without adding the priority level informationor the deletion possibility information may be employed. In such a form,the display control device 16 stores, in the HDD 46 in advance, prioritylevel tables indicating the priority level and deletion possibility foreach type of the drawing request information, as shown in Table 1 andTable 2 prepared in advance, and, in the sorting processing, the displaycontrol device 16 sorts the drawing request information stored in thebuffer 52 in the order of priority level on the basis of the prioritylevel tables.

Although the individual embodiments described above have been describedin terms of the case in which, in the sorting processing, every time thedisplay control device 16 receives the drawing request information, thedisplay control device 16 judges whether or not real-time responsivenesswill be lost in updating the display contents at the shared displaydevice 18, the present invention is not limited thereto, and a form inwhich whether or not real-time responsiveness will be lost in updatingthe display contents in the shared display device 18 is judged atpredetermined time intervals (for example, every one second) may beemployed.

Although the individual embodiments described above have been describedin terms of the case in which, in the sorting processing, the drawingrequest information stored in the buffer 52 is sorted in the order ofthe priority level when real-time responsiveness will be lost inupdating the display contents in the shared display device 18, thepresent invention is not limited thereto, and it is permissible toemploy a form in which, for example, the drawing request informationstored in the buffer 52 is sorted in the order of the priority levelevery time the display control device 16 receives the drawing requestinformation and stores it in the buffer 52, without judging whether ornot real-time responsiveness will be lost in updating the displaycontents in the shared display device 18.

Although the individual embodiments described above have been describedfor the case in which a FIFO buffer is employed as the buffer 52, thepresent invention is not limited thereto, and an other type of buffermay be employed as the buffer 52 so long as it is a buffer that iscapable of reading out the drawing request information in the order ofpriority level.

What is claimed is:
 1. A display control device that is connected to aplurality of input operation devices via a communication line and thatupdates display contents on a shared display device on the basis ofdrawing request information sent from the input operation devices, thedisplay control device comprising: a storage unit that stores multiplepieces of the drawing request information sent from the input operationdevices; a control unit that controls the shared display device, whereinthe control unit includes: a judgment part that judges as to whether ornot real-time responsiveness in updating the display contents in theshared display device is lost if the display contents are updated basedon the multiple pieces of the drawing request information stored in thestorage unit, and a sorting part that sorts the multiple pieces of thedrawing request information stored in the storage unit in order ofpriority level which is predetermined for each type of the drawingrequest information when the judgment unit judges that the real-timeresponsiveness is lost, wherein the control unit reads out the multiplepieces of the drawing request information from the storage unit in thesorted order when the judgment unit judges that the real-timeresponsiveness is lost, and controls the shared display device so thatthe display contents are updated based on the multiple pieces of thedrawing request information which are read out in the sorted order.
 2. Adisplay control device according to claim 1, wherein a predeterminedtype of the drawing request information stored in the storage unitindicates a possibility of deletion and can be deleted from the storageunit, excluding the most recent drawing request information, thepossibility of deletion is added to the drawing request informationtogether with the priority level.
 3. A display control device accordingto claim 1, wherein the drawing request information includes cursormovement information that indicates a cursor destination displayed onthe shared display device, wherein the cursor movement informationspecifies the cursor destination by an absolute position with referenceto a predetermined position on a screen indicated by the shared displaydevice.
 4. A display control device according to claim 3, wherein thedisplay control device is switched either to a first mode, in whichfirst cursor movement information that specifies the cursor destinationby absolute position with reference to a predetermined position on thescreen of the shared display device, is used as the cursor movementinformation, or to a second mode, in which second cursor movementinformation that specifies a next cursor destination at the shareddisplay device on the basis of an amount of cursor movement per unittime at the input operation devices with reference to a previous cursordestination, is used as the cursor movement information.
 5. A controlsystem comprising: a plurality of input operation devices that senddrawing request information for updating display contents at a shareddisplay device; a display control device according to claim
 1. 6. Adisplay control device according to claim 1, wherein the priority levelsare set to be higher for drawing request information indicating displaycontent of greater importance.
 7. A display control device according toclaim 1, wherein the drawing request information includes cursormovement information which indicates a cursor destination to bedisplayed on the shared display device, image drawing information fordrawing images generated at the input operation devices on the shareddisplay device, click information for executing an application, andemergency-message display information created at the input operationdevices for causing an emergency massage to be displayed on the shareddisplay device.
 8. A display control method, in which a plurality ofinput operation devices are connected via a communication line anddisplay contents in a shared display device are updated on the basis ofdrawing request information sent from the input operation devices, thedisplay control method comprising: a step of judging whether or notreal-time responsiveness in updating the display contents in the shareddisplay device is lost if the display contents are updated based on themultiple pieces of the drawing request information stored in a storageunit, a step of sorting the multiple pieces of the drawing requestinformation stored in the storage unit in order of priority level whichis predetermined for each type of the drawing request information whenit is judged that the real-time responsiveness is lost, a step ofreading out the multiple pieces of the drawing request information fromthe storage unit in the sorted order when it is judged that real-timeresponsiveness is lost, and a step of controlling the shared displaydevice so as to display that the display contents are updated based onthe multiple pieces of the drawing request information which are readout in the sorted order.